Organic EL (Electro Luminescence) devices are attracting attention as lighting equipment of future generations, and have been much studied.
An organic EL device is formed by laminating organic EL elements composed of substances such as organic compounds on a substrate such as a glass substrate or a transparent resin film. An organic EL element is a light emitting element that has an organic emission layer provided between an anode and a cathode. An organic emission layer is composed of layers such as a hole injection layer, a hole transport layer, an emission layer, an electron transport layer, and an electron injection layer.
An organic EL device is intrinsically a device that emits light upon application of a DC voltage. Specifically, an organic EL element has a junction of a p-doped semiconductor with an n-doped semiconductor, so that it is a device having a diode characteristic. Therefore, an organic EL element has polarities as described above and emits light only when power is supplied so that a p-doped semiconductor has a plus pole and an n-doped semiconductor has a minus pole and does not emit light in the contrary case. Consequently, when a commercial AC voltage is applied to organic EL elements, the organic EL elements light up at a half cycle of a forward voltage and black out at the other half cycle of a backward voltage, which may cause a perceptible flicker (blinking) in our eyes.
Thus, there would exist such a configuration in which a rectification circuit is added to an organic EL device. A patent document 1 specified below discloses an organic EL lighting equipment (hereinafter simply referred to as an organic EL device) provided with a rectification circuit. Though the organic EL device described in the patent document 1 uses an AC source as an external power source, it prevents a flicker (blinking) by a full-wave rectification in the rectification circuit. Further, an integral provision of the rectification circuit with organic EL elements is described as a realizable downsizing of the organic EL device.